In a semiconductor manufacturing apparatus, a liquid crystal production apparatus, an exposure apparatus and a substrate inspection apparatus (hereinafter collectively referred to as a “semiconductor manufacturing apparatus”), a horizontal articulated transfer robot is widely used to transfer a substrate such as a semiconductor wafer or a liquid crystal glass. The horizontal articulated robot includes a body, a plurality of arms connected to the body in multistage and a fork arranged at the tip end of the arms. The substrate is placed on the fork. The arms and the fork are configured to make rotation relative to each other. The substrate is transferred from one desired position to another by rotating the arms and the fork.
In the conventional horizontal articulated robot, motors as power sources for driving the arms and the fork and speed reducers are accommodated within the body. The torque of the motor is delivered to the corresponding arms or fork through transmission mechanisms such as pulleys and belts (see, e.g., JP2-24075A). The configuration in which all the motors are accommodated within the body as mentioned above can simplify the internal structures of the arms and, therefore, assists in making the arms smaller and thinner. If the arms become compact, they have an increased operating range within a limited narrow space like the interior of a semiconductor manufacturing apparatus.
With the configuration set forth above, however, the transmission mechanisms such as belts or the like become longer due to the increased distance between the motors and the driven objects. This makes it difficult to accurately drive the arms and the fork, which in turn impairs the operability of the arms and the fork. Therefore, the aforementioned configuration is unsuitable for use in an up-to-date semiconductor manufacturing apparatus in which a substrate is required to be transferred with high accuracy. Another problem of this configuration resides in that the internal structure of the body grows complex and the transmission mechanisms become lengthy with the number thereof increased.
As a solution to these problems, attempts have been made to arrange motors and speed reducers on or within arms, thereby simplifying transmission mechanisms and improving operability (see, e.g., JP2008-137115A, JP1-240288A, and JP2006-289555A). With the configuration in which the motors and the speed reducers are arranged on or within the arms, the distance between the motors and the driven objects becomes short. This helps improve the operability of the arms and the fork as compared with the configuration in which all the motors are accommodated within the body. Since, however, the motors and the speed reducers are arranged on or within the arms, the configuration noted just above suffers from problems in that the arms grow bigger and the motor for driving the arm closest to the body falls short of capacity, consequently impairing the operability.
In addition, the transfer robot for use in a semiconductor manufacturing apparatus is required to increase the number of substrates that can be transferred per unit hour. With a view to increase the number of substrates transferred by the robot, it has been proposed that a plurality of forks is provided in one set of arms (see, e.g., JP2002-184834A). In general, tubes for a fluid used in holding a substrate and cables for a sensor used in making sure accurate holding of the substrate are connected to the forks. The tubes and the cables extend from a body to the respective forks through the interior of the arms. For that reason, the arms need to have a space for appropriately dealing with the tubes and the cables connected to the forks as well as a space for accommodating the motors and the transmission mechanisms mentioned above. This is one of causes of increasing the size of the arms (see, e.g., JP2007-237342A).
As is apparent from the above, operability and compactness are required in the arms of the transfer robot particularly for use in the semiconductor manufacturing apparatus. Thus, a great deal of effort has heretofore been made to improve the shape and configuration of the arms.